The invention relates to a cooling system for a projector.
WO 2004/029 507 A1 discloses a projector that has a light source that is arranged in a projector housing, is capped at one or two ends and comprises a lamp or a burner, for example a discharge lamp in the form of a metal-halide lamp, and a reflector that reflects the light emitted by the light source in the direction of a front opening of the projector housing that can be sealed by a transparent cover element, for example a protective disk or lens disk.
In addition to radiating visible light beams, a burning light source also produces in its arc or filament invisible thermal radiation that lies in the infrared spectral range and is output by the following three processes to the surroundings of the light source:    a) the thermal radiation is partially absorbed by the components surrounding the light source, such as reflector, light source base and supply leads to the light source, and by the projector housing, which components thereby experience negative influence on their material properties and themselves act as secondary heat source,    b) thermal conduction takes place via the electric contacts and via the ceramic body of the light source base, and    c) the ambient air of the light source is heated up, rises upward and entrains cooler air upward from below in a convective cooling process.
In order to support the last-named process and to provide a projector of high power with a compact design, the projector housing disclosed in WO 2004/029 507 A1 comprises an upper, cylindrical projector housing part and a lower projector housing part that is of cuboidal design and on which ventilation shafts with mutually separate ventilation ducts are arranged. The ventilation ducts are separated from one another by fins that have inside the ventilation shaft a first fin section adjacent to the air entrance openings, and a second fin section, which is adjacent to the air exit openings and is bent away from the first fin section.
U.S. Pat. No. 5,172,975 A discloses a projector with a light source, a reflector and a light exit opening in a cylindrical projector housing on which there are formed ventilation ducts that likewise circulate for convective cooling of the surroundings of the light source outputting heat, and are delimited by fins. The fins are bent away outside the cylindrical projector housing and are flanged at their ends so that, firstly, light is prevented from exiting from the interior of the projector housing and, secondly, the flow of air is directed away perpendicularly from the projector housing.
U.S. Pat. No. 1,758,290 A discloses a projector housing with ventilation shafts, which are arranged on the housing walls, have ventilation ducts separated from one another and are separated from one another by fins such that uniform ventilation ducts are produced via which cooling air flows into the interior of the projector housing. The ends, projecting into the interior of the projector housing, of the fins above and below the optical axis of the projector are bent away again in respectively opposite directions such that the ends of the fins arranged above the optical axis are directed toward the underside of the projector housing, while the ends, arranged below the optical axis, of the fins are directed toward the top side of the projector housing, and the two sections are connected to one another in a central horizontal part such that improved circulation of cooling air through the projector housing is attained by the different alignment of the ends, located in the interior of the projector housing, of the fins.
In addition to the thermal radiation output by the light source, heat from further electric and electronic components, such as an ignitor and the electric supply leads, is also output to the interior of the projector housing, which is likewise to be dissipated by a convective cooling process.
Another problem in the dissipation of heat from a projector housing lies in the fact that, if the projector is tilted with respect to the horizontal, the convective flow of air is guided into higher parts of the projector housing, so that local overheating and, as a consequence, damage to or destruction of components can easily occur.
In order to provide sufficient space for the convective flow of air and to dissipate the heated air more effectively to the surroundings of the projector, the projector housings of known projectors have a larger volume and their outer surfaces are strongly ribbed in order to increase the area of the housing which outputs the heat.